Efficacy Of A Recombinant Pseudorabies Virus Expressing The GP5 Of Porcine Reproductive And Respiratory Syndrome Virus

Porcine reproductive and respiratory syndrome (PRRS) is one of the mostimportant infectious diseases in pigs, causing late-term reproductive failure in sowsand severe pneumonia in neonatal pigs. The disease is caused by PRRS virus(PRRSV), a member of the Arteriviridae family. Current vaccines against PRRSVhave some drawbacks. Killed vaccines have been proved to be less effective inprevention from both infection and disease. Modified live vaccines typically provideprotection against clinical disease but not infection in some cases. Additionally, livePRRSV vaccines are likely to revert to virulence. Development of safe and efficaciousvaccines against PRRS remains a big challenge. GP5 is the major envelopeglycoprotein of the virus.To research a safer and more effective vaccine, a recombinant PRV harboringPRRSV GP5 gene, designated as rPRV-GP5, was inoculated in BALB/c mice andpigs.To analyse the immune responses induced by a recombinant pseudorabies virusexpressing the GP5(rPRV-GP5)of porcine reproduction and respiratory syndromevirus(PRRSV) in animals. One hundred BALB/c mice were randomly divided intothree groups. Sixty mice in Group 1 were each inoculated intranasally with10^5.0TCID₅₀ of rPRV-GP5, twenty mice in Group 2 each inoculated intranasally with10^5.0TCID₅₀ of Bartha-K61, twenty mice in Group 3 as non-vaccinated control.Spleen lymphocytes were isolated every week after the immunization to assay thecytokines mRNA expression level by RT-PCR. The PRRSV specific T lymphocyteproliferation test were used at the end of the eighth week after immunization. Thelung,intestine,fecal fluid and serum were taken to assay the specific IgA or IgGagainst GP5 with Indirect Immunofluorescent Assay. The results shown, the specificIgA and IgG antibodies against GP5 first time were detected at the fourth week afterinoculation. The last time to detect the two antibodies was at seventh week and tenthweek after inoculation. Animals in Group 1 induced higher expression of IFN-γsince16h after incubation. The level of expression of IL-4 was obviously lower than the IFN-γduring the incubation. The result of the lymphocyte proliferative assayindicated that the response of T-lymphocytes in spleen was higher in rPRV-GP5immunized group than the Bartha-K61 immunized and control group (P＜0.05). All theresults shown that the mice inoculated rPRV-GP5 can effectively induce humourimmune and cell immune response against PRRSV.Fifteen PRV-and PRRSV-negative healthy piglets were assigned to one of 3groups (5 pigs per group). Animals in Group 1 were each inoculated intranasally(i.n)10^7.0 PFU of rPRV-GP5; Group 2 were each inoculated i.n with 10^7.0 PFU of its parentBartha-K61; Group 3 was served as non-vaccinated control. Serum were taken toassay the specific IgG against GP5 with Indirect Immunofluorescent Assay. PBMCswere were isolated on the 4～7 week after the immunization for lymphocyteproliferative assay. The results shown, the specific IgG antibodies against GP5 firsttime were detected at the fourth week after inoculation. The result of the lymphocyteproliferative assay indicated that the response of T-lymphocytes in spleen was higherin rPRV-GP5 immunized group than the Bartha-K61 immunized and control group(P＜0.05).In summary, the rPRV-GP5 is a good candidate recombinant virus vaccine tocontrol PRRS and pseudorabies.